Still More Problems with Infared LED
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Posts: 46,084
A while back, I posted a note about trying to get an Infared LED to work.
Several people posted responses, and I appreciate all the help everyone
offered.
I'm still not able to get the Infared LED to work. I can't see it using my
camcorder - so I assume it is not working. I tried hooking up the detector
to a regular LED, but it stays lit all the time.
As I said before, I bought it from Radio Shack ( Cat No. 276-142 - Infared
Emitter and Detector, 1 pr. ) The specs on the back indicate a Reverse
Voltage of 2V and Continous Forward Current of 40mA. I am using a 6v
supply. I am making sure that the longer leg ( Anode ) is connected to ( +
). It does not say anything about forward current. I have also made a 555
circuit that is suppose to generate 38kHz. The following site has project
for an IR Encoder/Decoder with the following program to test the 555
circuit. When I ran the BS2 program, the debug statement was giving me a
value of around 3850.
======================
'Basic Stamp II Freq Counter
O555 con 7
freq var word
Loop:
count O555,100,freq
debug dec5 freq*10,cr
goto Loop
' Source from: www.verinet.com/~dlc/projects/botproj.htm
' 555 Based IR Proximity Detector
======================
During one of my tests, I placed a resistor and a regular LED between the
(+) and (-). I measured the voltage across the the LED and it was somewhere
around 1.2 volts. I then substitued my IR LED and again measured the
voltage - which was around 5.87 volts.
How can I tell if I have destroyed my IR LED ? If I put a regular LED in
series with the IR LED, the regular LED still lights up; and if I reverse
the pins on the IR LED, my regular LED will not light. I have two ( 2 ) IR
LEDs to test with. When I put a regular LED in the 555 circuit, and measure
the voltage, I get 1.07 volts. If I replace the regular LED with IR LED(1),
I get 1.07 volts; and with IR LED(2), I get .58 volts.
For those people that have done IRPD, what are you using for your emitter
and detector. Should my Radio Shack Cat No. 276-142 be able to do the job,
or should I be using something else ? ( if something else is being used,
what part number and company are you using ? )
I have several examples of 555 circuits that indicate to put an IR LED in
the circuit, but I do not have any circuits that gives reference to a Radio
Shack Cat No. 276-142. Has anyone else specificly used this Radio Shack
part number in a IRPD circuit ?
I have the 1980 Ed of Mims' Engineer's Notebook; pg 115 has LED Transmitter
with 555 timer; www.verinet.com/~dlc/irbot/irbot.htm ,
www.hut.fi/Misc/Electronics/circuits/irdetector.html , and
http://home.att.net/~eliel/detector.htm - they all talk about infared
detectors - just can't get the ones I bought to work.
Any additional help would be appreciated.
Thanks,
Bryan Smith
Several people posted responses, and I appreciate all the help everyone
offered.
I'm still not able to get the Infared LED to work. I can't see it using my
camcorder - so I assume it is not working. I tried hooking up the detector
to a regular LED, but it stays lit all the time.
As I said before, I bought it from Radio Shack ( Cat No. 276-142 - Infared
Emitter and Detector, 1 pr. ) The specs on the back indicate a Reverse
Voltage of 2V and Continous Forward Current of 40mA. I am using a 6v
supply. I am making sure that the longer leg ( Anode ) is connected to ( +
). It does not say anything about forward current. I have also made a 555
circuit that is suppose to generate 38kHz. The following site has project
for an IR Encoder/Decoder with the following program to test the 555
circuit. When I ran the BS2 program, the debug statement was giving me a
value of around 3850.
======================
'Basic Stamp II Freq Counter
O555 con 7
freq var word
Loop:
count O555,100,freq
debug dec5 freq*10,cr
goto Loop
' Source from: www.verinet.com/~dlc/projects/botproj.htm
' 555 Based IR Proximity Detector
======================
During one of my tests, I placed a resistor and a regular LED between the
(+) and (-). I measured the voltage across the the LED and it was somewhere
around 1.2 volts. I then substitued my IR LED and again measured the
voltage - which was around 5.87 volts.
How can I tell if I have destroyed my IR LED ? If I put a regular LED in
series with the IR LED, the regular LED still lights up; and if I reverse
the pins on the IR LED, my regular LED will not light. I have two ( 2 ) IR
LEDs to test with. When I put a regular LED in the 555 circuit, and measure
the voltage, I get 1.07 volts. If I replace the regular LED with IR LED(1),
I get 1.07 volts; and with IR LED(2), I get .58 volts.
For those people that have done IRPD, what are you using for your emitter
and detector. Should my Radio Shack Cat No. 276-142 be able to do the job,
or should I be using something else ? ( if something else is being used,
what part number and company are you using ? )
I have several examples of 555 circuits that indicate to put an IR LED in
the circuit, but I do not have any circuits that gives reference to a Radio
Shack Cat No. 276-142. Has anyone else specificly used this Radio Shack
part number in a IRPD circuit ?
I have the 1980 Ed of Mims' Engineer's Notebook; pg 115 has LED Transmitter
with 555 timer; www.verinet.com/~dlc/irbot/irbot.htm ,
www.hut.fi/Misc/Electronics/circuits/irdetector.html , and
http://home.att.net/~eliel/detector.htm - they all talk about infared
detectors - just can't get the ones I bought to work.
Any additional help would be appreciated.
Thanks,
Bryan Smith
Comments
>A while back, I posted a note about trying to get an Infared LED to work.
>Several people posted responses, and I appreciate all the help everyone
>offered.
>
>I'm still not able to get the Infared LED to work. I can't see it using my
>camcorder - so I assume it is not working. I tried hooking up the detector
>to a regular LED, but it stays lit all the time.
Try reversing the leads on the LED, then measure the voltage drop across
the LED. The voltage reading that you mentioned that you got (5.87V) sure
makes me think that the LED is backwards.
dwayne
Dwayne Reid <dwayner@p...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 17 years of Engineering Innovation (1984 - 2001)
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